PURPOSE: To obtain advantageously the titled compound useful as an antidepressive, etc., by reacting 2-N-substituted-aminothiophenol with a novel 2-acetoxy-3- halo-3-substituted-propionic acid, subjecting the prepared novel intermediate to ring closure.

CONSTITUTION: A compound shown by the formula 1 is reacted with a novel substance shown by the formula 2 (X is halogen) in the presence of a small amount of a base such as pyridine, collidine, etc., to give a novel substance shown by the formula 3, which is subjected to ring closure in the presence of preferably a small amount of acetic anhydride in a solvent such as benzene, toluene, xylene, etc. under reflux to give a compound shown by the formula 4 useful as a tranguilizer or coronary vasidilator only by two processes from the raw materials. Since the novel substance shown by the formula 3 obtained as an intermediate has already contained acetyl group, its acetylation is not required. Since it is a free acid, hydrolysis is not required. Consequently, the compound shown by the formula 4 may be derived by subjecting directly the intermediate to ring closure.